Swift J1658.2-4242: Possible pulsar periodicity detected

ATel #11311; J. A. Kennea (PSU)
on 16 Feb 2018; 20:04 UT
Credential Certification: Jamie A. Kennea (kennea@astro.psu.edu)

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We report on analysis of all the current Windowed Timing mode data taken on the newly discovered Galactic Transient, Swift J1658.2-4242 (GCN #22416, GCN #22417, GCN #22419, ATEL #11310, ATEL #11306, ATEL #11307). We have performed a broad band periodicity analysis on data totaling an exposure of 1629s, containing 8093 X-ray events, utilizing a Z²₁ search. We find the most significant peak in the Z²₁ periodogram is at P = 8.7274 +/- 0.0078 s.

Utilizing the FTOOLS "powspec" command, we confirm the presence of the peak at ~0.115 Hz, with no obvious broadening , suggesting that this is not a QPO but rather a discrete period. Therefore we suggest that this period, if real, is the signature that Swift J1658.2-4242 contains a pulsar, constraining the system type to being likely an accreting pulsar, e.g. a previously undiscovered Be/X-ray binary system.

Deeper TOO observations are encouraged in order to confirm the presence of this period.